Organ walls are composed of several layers: the mucosa (the surface layer), the submucosal, the muscularis (muscle layer), and the serosa (connective tissue layer). In gastrointestinal, colonic, and esophageal cancer, small polyps or cancerous masses form along the mucosa and often extend into the lumens of the organs. Conventionally, that condition has been treated by cutting out a portion of the affected organ wall. This procedure, however, may cause extensive discomfort to patients, and posed health risks. Recently, physicians have adopted a minimally invasive technique called endoscopic mucosal resection (EMR), which removes the cancerous or abnormal tissues (polyps) or normal tissues, keeping the walls intact.
EMR is generally performed with an endoscope, which is a long, narrow tube equipped with a light, video camera, and channels to receive other instruments. During EMR, the endoscope is passed down the throat or guided through the rectum to reach a tissue in the affected organ or otherwise targeted tissue. The distal end of the endoscope, further equipped with a cap that has a small wire loop, is guided towards the abnormality. Once there, a suction pump attached to the tube is started to draw the abnormality towards the endoscope cap. When the tissue is sufficiently drawn into the cap, the wire loop closes around the tissue, resecting it from the organ wall. Subsequently, excised tissue may be extracted by, e.g., the vacuum, for examination or disposal.
Certain polyps, such as pedunculated polyps, may be characterized by a stalk attached to the mucosal layer. Drawing such polyps into the cap without drawing in any other tissue is readily accomplished. Certain other polyps, such as sessile polyps, however, may exhibit a broad base and they lay flat on the mucosal surface, devoid of a stalk. It is often difficult to grasp these polyps without drawing in a part of the muscularis layer.
To overcome this problem, saline solution is typically injected beneath the target tissue to raise the mucosal tissue and create a buffer layer. The raised tissue can then readily be severed with a resection loop, often in several segments (segmental resection) depending on the size and location of the tissue.
In addition, the depth of the cut made by the wire loop cautery is critical. As discussed above, if the cut is too deep, the muscularis layer may be injured, which may further cause a perforation. Conversely, a cut too shallow may not remove enough of the affected tissue and therefore may require additional procedures or worse, contribute to the development of metastatic cancer. Typically, more than 2 mm of cancerous tissue clearance is required to assure complete removal. EMR, as performed with conventional devices and methods, may result in complications such as perforation, bleeding, and/or strictures.
Therefore, there exists a need for an improved endoscopic mucosal resection loop that effectively resects pedunculated and sessile polyps or other tissues without damaging the surrounding tissue or muscle layers of the organ.